1. Field of the Invention
The present invention relates generally to mechanical power pants. More particularly, the invention concerns a low emission power plant which comprises a modified diesel engine component and a modified turbocharger component which has a relatively low turbocharger aspect ratio. The diesel engine component is a modification of a two-stroke, uniflow-scavenge diesel engine design and includes an exhaust valve cam of unique design that has a cam profile which results in a later-than-normal exhaust valve opening and an earlier-than-normal valve closing so that the time during which the exhaust valve remains open is shorter than normal thereby causing a substantially greater volume of residual gases to remain in the combustion chamber following the scavenge stroke.
2. Discussion of the Prior Art
Mechanical power plants embodying diesel engines are widely used in both on-road and off-road applications. Such power plants have always been popular for use in large trucks. However, such power plants have also been used extensively for off-road applications such as in earth moving equipment, in road graders and in stationary applications in connection with water and oil well drilling and pumping apparatus and many other applications.
Diesel engines are designed to operate on the two-stroke or on the four-stroke principle as are gasoline engines. In the two-stroke engine, intake and exhaust take place during part of the compression. A four-stroke engine requires four piston strokes to complete an operating cycle and thus, during one-half of its operation, the four-cycle engine functions merely as an air pump. The present invention is directed primarily, but not exclusively, to use with two-stroke engines.
While diesel engines are durable, reliable, and economical, the control of emissions from such engines has presented substantial problems. Accordingly, extensive research has been directed toward making the diesel engine burn ever cleaner so as to meet seemingly ever increasing emission control requirements imposed by state and federal legislation. In this regard, substantial experimentation has been in the areas of electrical and electronics monitoring and control. However, the thrust of the present invention is directed to effectively decreasing emissions from diesel engine power plants by mechanical means using, for the most part specially modified, generally commercially available components.
As will be better appreciated from the discussion which follows, emissions from the improved mechanical power plant of the present invention are quite low. For example, the current legislatively mandated levels of hydrocarbon emissions require that hydrocarbon emissions be no greater than 1.3 grams per horsepower-hour (g/bhp-hr.). Testing of the novel apparatus of the present invention by an independent testing agency has shown the hydrocarbon emissions to be on the order of 0.54 g/bhp-hr, which is obviously substantially less than the generally accepted regulatory level. Similarly, the applicable legislatively man-dated limit for particulate emissions is set at 0.1 grams per brake horsepower-hour (g/bhp-hr.). When the apparatus of present invention was appropriately coupled with a catalytic converter of conventional design and was applied to a typical two-stroke engine, testing of the assemblage revealed that particulate emissions were on the order of 0.08 g/bhp-hr,. which is well within the limits imposed by the retrofit standard. Additionally, while the mandated limit for carbon monoxide emissions is 15.5 g/bhp-hr. testing of the apparatus of the present invention shows carbon monoxide emissions from the apparatus to be less than 0.6 g/bhp-hr. Finally, testing of the power plant of the invention has also revealed that during normal operation the NOx emissions from the power source were 10.2 g/bhp-hr, which is comfortably lower than the legislatively mandated level of 10.7 g/bhp-hr.